全文获取类型
收费全文 | 1017篇 |
免费 | 46篇 |
国内免费 | 4篇 |
专业分类
化学 | 649篇 |
晶体学 | 3篇 |
力学 | 40篇 |
数学 | 254篇 |
物理学 | 121篇 |
出版年
2023年 | 11篇 |
2021年 | 34篇 |
2020年 | 38篇 |
2019年 | 25篇 |
2018年 | 23篇 |
2017年 | 16篇 |
2016年 | 34篇 |
2015年 | 33篇 |
2014年 | 34篇 |
2013年 | 49篇 |
2012年 | 63篇 |
2011年 | 61篇 |
2010年 | 34篇 |
2009年 | 31篇 |
2008年 | 31篇 |
2007年 | 51篇 |
2006年 | 62篇 |
2005年 | 44篇 |
2004年 | 28篇 |
2003年 | 29篇 |
2002年 | 25篇 |
2001年 | 17篇 |
2000年 | 10篇 |
1999年 | 8篇 |
1998年 | 8篇 |
1997年 | 6篇 |
1996年 | 8篇 |
1995年 | 5篇 |
1994年 | 10篇 |
1992年 | 11篇 |
1991年 | 5篇 |
1984年 | 5篇 |
1983年 | 6篇 |
1981年 | 5篇 |
1980年 | 5篇 |
1977年 | 6篇 |
1967年 | 4篇 |
1958年 | 4篇 |
1957年 | 6篇 |
1956年 | 6篇 |
1930年 | 5篇 |
1922年 | 6篇 |
1908年 | 4篇 |
1903年 | 4篇 |
1902年 | 4篇 |
1899年 | 5篇 |
1898年 | 4篇 |
1894年 | 5篇 |
1888年 | 5篇 |
1884年 | 4篇 |
排序方式: 共有1067条查询结果,搜索用时 859 毫秒
991.
992.
993.
Baoling Wang Michael Forster Eduard Preis Huan Wang Yuguang Ma Ullrich Scherf 《Journal of polymer science. Part A, Polymer chemistry》2009,47(19):5137-5143
In this study, a simplified route to synthesize soluble, spiro‐bridged ladder‐type poly(p‐phenylene)s (spiro‐LPPP) was developed. The new, simplified synthesis route for spiro‐LPPP involves two reaction steps: a single‐stranded precursor polymer containing diaryloylbenzene building blocks was obtained by the Suzuki reaction, followed by a subsequent twofold cyclization cascade using methanesulfonic acid to form the target spiro‐LPPP. Spiro‐LPPP shows a well‐defined chemical structure, high molecular weight (Mn of 17,500 g/mol with a polydispersity index of 2.0), excellent thermal stability (5% weight loss at 370 °C), and good solubility in common organic solvents. Spiro‐LPPP emits blue light (λmax,em = 455 nm) with the high solution PL quantum yield (94%). The spectral properties of spiro‐LPPP in the solid state are very similar to the solution properties, thus indicating a low degree of intermolecular aggregation. After annealing a thin film of spiro‐LPPP to 120 °C in air for 3 to 24 h, its emission spectrum is unchanged, reflecting excellent thermooxidative stability. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5137–5143, 2009 相似文献
994.
Eduard v. Weber 《Mathematische Annalen》1894,44(4):458-472
Ohne Zusammenfassung 相似文献
995.
B. Schöndorff H. Jessen-Hansen Ivar Bang Matthew Steel William J. Gies F. G. Benedikt V. C. Myers W. Wiechowski Frank P. Underhill Israel S. Kleiner Eduard Strauss H. Schulz Emil Osterber Charles G. R. Wolff Arthur Konschegg Emil Abderhalden C. Funk G. Modrakowski Leo Hess R. Engeland und C. A. Herter 《Fresenius' Journal of Analytical Chemistry》1909,48(11):721-726
Ohne Zusammenfassung 相似文献
996.
Iryna S. Zhylenko Pavlo V. Solntsev Eduard B. Rusanov Alexander N. Chernega Konstantin V. Domasevitch 《Acta Crystallographica. Section C, Structural Chemistry》2008,64(4):o237-o241
1,4,5,8‐Tetramethylpyridazino[4,5‐d]pyridazine trihydrate, C10H12N4·3H2O, (I), and 1,2,3,6,7,8‐hexahydrocinnolino[5,4,3‐cde]cinnoline tetrahydrate, C12H12N4·4H2O, (II), exhibit exceptional functionality of the condensed N4‐heteroaromatic frame as a symmetric acceptor of four hydrogen bonds [N...O = 2.843 (2)–2.8716 (10) Å]. Thus, all the N atoms of the electron‐deficient and highly π‐acidic polynitrogen heterocycles function as lone‐pair donors. In (I), all the molecular components lie on or across special positions; the site symmetry is 2/m for the organic and m2m and m for the two water molecules. In (II), the organic polycycle lies across a crystallographic inversion center. Both structures involve a hydrogen‐bonded centrosymmetric water–pyridazine dimer as the basic supramolecular unit, which is integrated into two‐dimensional [in (I)] and three‐dimensional [in (II)] hydrate frameworks by hydrogen bonding with the additional water molecules [O...O = 2.744 (2)–2.8827 (19) Å]. The hydrate connectivity exists in the form of an (H2O)3 trimer in (I) and as a one‐dimensional zigzag (H2O)n chain in (II). 相似文献
997.
Eduard Donath 《Fresenius' Journal of Analytical Chemistry》1873,12(1):325-327
Ohne Zusammenfassung 相似文献
998.
Eduard Boďa 《Mathematica Slovaca》2008,58(2):173-176
Let (R,m) = k[x
1,..., x
n
](x
1,...,x
n
) be a local polynomial ring (k being an algebraically closed field), and Q:= (F
1,..., F
r
)R be a primary ideal in R with respect to a maximal ideal m ⊂ R. In this short note we give a formula for the multiplicity e
0 (QR/(F
1)R, R/(F
1)R).
The author was supported by the grant No. 1/0262/03) of the Slovak Ministry of Education. 相似文献
999.
In this paper we define the concept of quaternionic submersion, we study its fundamental properties and give an example.
相似文献
1000.
Eduard Maru?i?-Paloka Igor Pa?anin 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》2007,24(5):81-99
In this paper we study the flow of incompressible Newtonian fluid through a helical pipe with prescribed pressures at its
ends. Pipe’s thickness and the helix step are considered as the small parameter ɛ. By rigorous asymptotic analysis, as ɛ→
0 , the effective behaviour of the flow is found. The error estimate for the approximation is proved. 相似文献